Medical Abbreviation SER: Serum

SER (or S) stands for serum – the liquid component of blood after clotting and removal of cells (RBCs, WBCs, platelets) and fibrinogen.

Serum vs. Plasma

• Serum: No clotting factors (fibrinogen removed); obtained after clotting (red-top or SST tube).
• Plasma: Contains fibrinogen; obtained with anticoagulant (EDTA, heparin, citrate).

Common Uses

• Chemistry panels (electrolytes, glucose, lipids, enzymes, proteins).
• Endocrine (hormones, tumor markers).
• Serology (antibodies, antigens).
• Therapeutic drug monitoring.

Key Point

Serum is the default specimen for most clinical chemistry tests. Always verify tube type and processing requirements for each assay.